(a) Field of the Invention
The present invention relates to a method for relaying data between a base station and a terminal or between terminals.
(b) Description of the Related Art
In order to support proximity-based services in a wireless communication system, a method for establishing a direct link between terminals is under discussion in IEEE 802.11 (pre-association discovery, PAD), IEEE 802.15 (TG8, peer aware communication, PAC), IEEE 802.16 (GRIDMAN TG) and 3GPP (D2D proximity-based service, ProSe), and the like.
Recently, services have been provided through establishment of direct links between terminals as proximity-based services (LTE device to device proximity discovery) including public safety, disaster relief, non-public safety (or commercial), and the like.
In order to establish a direct link between terminals, each neighbor terminal determines a possibility of forming a direct link through searching. When formation of a direct link is possible, each terminal forms a direct link with a neighbor terminal to directly exchange data without the help (relaying) of a base station (BS). However, in a state in which a terminal establishes a direct link and exchanges data through the direct link, if the terminal moves, data exchange through the direct link may be impossible or efficiency may deteriorate.
In this case, the terminal may exchange data with the help of a BS or any other terminal. In a case in which one of two terminals connected through a direct link moves out of a service area of a BS, a terminal located within the service area of the BS may help the terminal outside the service area of the BS exchange data with a BS.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.